1. Field of the Invention
The present invention relates to an apparatus for fabricating a semiconductor device using plasma, and more particularly, to an apparatus for fabricating a semiconductor device using plasma, whereby the semiconductor device fabricating process using plasma provides significantly greater uniformity.
2. Description of the Related Art
Semiconductor devices such as dynamic random access memories (DRAM) and application specific integrated circuits (ASIC) generally comprise a plurality of electronic devices, for example, MOS transistors, capacitors, or resistors, which are formed on a semiconductor substrate. In recent years, due to the rapid development of the information communications industry and the wide use of information mediums such as computers, semiconductor devices require high speed operation as well as large-capacity storage capability. Thus, semiconductor device fabrication techniques for improving integration, reliability, and response speed of semiconductor devices have been developed.
When fabricating a semiconductor device, plasma may be used in the deposition process for forming a variety of layers on the surface of the semiconductor substrate or an etching process for forming a desired pattern. There are essentially two categories of etching processes: a wet etching process in which the portion to be etched is selectively removed by inducing a chemical reaction using a chemical solution; and a dry etching process in which the portion to be etched is removed using free electrons or ions of a reaction gas generated in a plasma state created by supplying radio frequency (RF) power. In particular, the dry etching process becomes more preferred as the semiconductor device becomes more highly integrated.
A conventional etching apparatus for fabricating a semiconductor device using plasma will now be described with reference to FIGS. 1 through 3. The apparatus shown in FIGS. 1 through 3 comprises a process chamber 11, a first electrode 12, a second electrode 16, and a confinement ring assembly 14. In the process chamber 11, an etching process is performed. To the first electrode 12 is transferred a radio frequency (RF) power from an RF power supply unit 18. A semiconductor substrate 15 is placed on the second electrode 16 and a reaction gas is supplied thereto from a gas supplying unit 17 to perform an etching process. As shown in FIG. 2, the confinement ring assembly 14 includes a first confinement ring 14_1, a second confinement ring 14_2, and a third confinement ring 14_3, which are connected to a confinement ring support unit 13. The first confinement ring 14_1, the second confinement ring 14_2, and the third confinement ring 14_3 are moved in a vertical direction, so that plasma pressure in the area where the semiconductor substrate 15 is placed can be adjusted.
FIG. 3 is a plane view of the confinement ring assembly 14 in a state where the confinement ring support unit 13 is removed from the apparatus of FIG. 1. As shown in FIG. 3, the confinement ring assembly 14 surrounds the first electrode 12. In other words, the first confinement ring 14_1, the second confinement ring 14_2, and the third confinement ring 14_3 surround the first electrode 12 and are separated from one another in the vertical direction.
The recent trend has been to increase the diameter of semiconductor substrates on which semiconductor devices are formed, thereby reducing the fabrication costs. For example, semiconductor devices have been fabricated using a silicon wafer having a diameter of 300 mm (12 inches) instead of a silicon wafer having a diameter of 200 mm (8 inches). As the diameter of semiconductor substrates increases, it is more difficult to ensure the uniformity of a semiconductor device fabricating process when fabricating semiconductor devices using the silicon wafer having the diameter of 300 mm compared to the case of fabricating semiconductor devices using the silicon wafer having the diameter of 200 mm. In particular, when etching a semiconductor substrate having a large diameter on which multiple layers are formed, i.e., when etching a semiconductor substrate having a large diameter on which multiple layers are formed using the conventional etching apparatus for fabricating a semiconductor device using plasma, it is very difficult to uniformly etch the lower part of a layer to be etched. Accordingly, uniformity in an etching process cannot be guaranteed.